Does WM_ERASEBKGND validate the area it erases?

When I does something like resizing my Window, a WM_ERASEBKGND message is sent followed by a WM_PAINT message.
The WM_ERASEBKGND (default) handler will erase the background, and the WM_PAINT handler will draw the foreground.

My question is, does the WM_ERASEBKGND handler validates the area it erases, I mean if it validates it then the WM_PAINT handler won't draw anything because the area is now validated.